Error for inverse dynamic analysis

I was trying to let the pelvis go through the given four points(quote from Egress Example) based on the freeposture, But if I let the “InverseDynamics” run I get this Error:
ERROR(OBJ.MCH.MUS4) : U:/E…n/A…y/E…d/A…n/E…s/S…l/StandingModel.Main.any : Study.InverseDynamics :Muscle recruitment solver : solver aborted due to singular KKT matrix.
I read the former posts, but still cannot solve the problems.
So I do ask for the possible solutions.

Best regarts

Hi Elisabeth

These drivers has not a reaction applied to them


Change this to be


The drivers in the egress example has no reaction on becuase they use ground reactions to make the balance. If you only carry over the pelvis motion to the freeposture model you will be missing these reactions, and then you have to make them in the pelvis instead.

Best regards

Hi Søren,
Thank you so much for your replying.
I turned all the reaction type of pelvis to On, but still have the same error,when doing the inverse dynamic analysis.
I am wondering what is the singular KKT matrix about? and any other reasons for the error?

Best regarts

Hi Elizabeth,

The KKT error means that the muscle recruitment solver failed to resolved the dynamic equilibrium equations.

Usually this would happen if there is a missing reaction to the world …

Please try to swicth on the muscles in the model this might resolve the problem?

The freeposture model is meant to display the various dof in the model and drive these by joint drivers, it is not meant to run inverse analysis on because it is not equipped with muscles and there are no loads applied.

Best regards